Wire grid polarizers can be used to divide light into two different polarization states. One polarization state can pass through the wire grid polarizer and the other can be absorbed or reflected. The effectiveness or performance of wire grid polarizers is based on a very high percent transmission (e.g. high Tp) of one polarization (e.g. p-polarization) and minimal transmission (e.g. low Ts) of an opposite polarization (e.g. s-polarization). It can be beneficial to have high contrast (Tp/Ts). The percent reflection (Rs) of the opposite polarization (e.g. s-polarization) can also be an, important indicator of polarizer performance.
Wires of wire grid polarizers, especially for polarization of visible or ultraviolet light, can be small and delicate with nanometer-sized pitch, wire-width, and wire-height. Water can condense or drop only onto limited portions of a wire grid polarizer. Because the water can be in one channel but not in an adjacent channel, forces in the water can cause wires to topple over, thus damaging the wire grid polarizer. Wire grid polarizer performance can also degrade by corrosion. Water can condense onto the wire grid polarizer and wick into narrow channels between wires due to capillary action. The water can then corrode the wires. Corroded regions can have reduced contrast, changed Rs, or can fail to polarize at all. Wire grid polarizers can be damaged by handling. Wires can topple-over as a user handles the wire grid polarizer.
Wire grid polarizers are used in systems (e.g. computer projectors, semiconductor inspection tools, etc.) that require high performance. Small defects in the wire grid polarizer, such as corroded or collapsed wires, can significantly degrade system performance (e.g. distorted image from a computer projector). Therefore, it can be important to protect the wires.